1. Field of the Invention
The invention concerns a ring binder mechanism with a housing having a C or U-shaped cross section with spring elastic spreadable flanks for two carrier rails, which on their longitudinal edges facing each other (inward facing) lie against each other to form a linkage or articulation axis and with their longitudinal edges facing away from each other (outward facing) engage in bearing grooves of the housing flanks, and with at least two half-rings rigidly connected with the carrier rails in a defined longitudinal spacing, preferably extending through openings in the housing wall and pair-wise cooperating to form a ring, wherein the carrier rails and the linkage axis, taking along the half-rings, are limitedly pivotable relative to each other between an open position and a closed position under the influence of, or overcoming the influence of, a spring force produced by bending open the housing flanks, and with at least one locking element movable relative to the housing and to the carrier rails, preferably pretensioned in the direction of the closed position under the influence of at least one locking spring, which in the locked position blocks the pivot path of the carrier rails about the linkage axis and is supported against at least one bearing for receiving locking forces and which in the open position unblocks the pivot path of the carrier rails.
2. Description of Related Art
In ring binder mechanisms, it is known to secure the organizing half-rings to carrier rails that are encompassed by a housing of a spring elastic material. The carrier rails are introduced in the housing in such a manner that they can assume two rest positions, an open and a closed position. The housing functions as a spring element, which fixes the half-rings in their open position and in their closed position. In the area of the inner longitudinal edges of the carrier rails there are engaging pieces or locking means, which ensure that the two carrier rails always lie edge-to-edge along these longitudinal edges. Therein the carrier rails have the function of a toggle lever held springingly at the outer edges. In conventional ring binder mechanisms, the opening and closing of the rings occurs directly via the half-rings. In order to achieve sufficient pretension and closure forces, a relatively large spring force is necessary in the area of the housing. The necessary operating forces are correspondingly large. The larger these forces, the larger also the danger of injury occurring upon closure at the points where the ring halves contact. In addition, since the closing forces are realized exclusively elastically, it often occurs that in response to a corresponding force, for example, upon falling onto the floor, the rings open by themselves, so that the stationary located there-between can fall out.
In order to overcome this disadvantage, it is known (U.S. Pat. No. 6,840,695), to secure the rings in their closed position by means of a locking element, which is displaceable relative to the housing and to the carrier rails parallel to the linkage axis via a locking rod and which in the closed position engages in a free space formed between the carrier rails and the housing wall with blockage of the pivot path of the carrier rails, and in the open position frees the pivot path. The half-rings are held in the closed position via a locking element that is held in a pretensioned position acting against the carrier rails, wherein the housing wall lying opposite to the carrier rails functions as a bearing for the locking element and for receiving the reaction forces corresponding to the locking forces.
In this ring binder mechanism, it is unavoidable that large manufacturing tolerances occur between the housing wall and the carrier rails, which must be compensated for by a wedge-shaped locking element. For this reason, the locking elements have relatively steep wedge surfaces, which are detrimental to the establishment of high locking forces between the housing walls and the carrier rails. If in such a case multiple locking elements are provided rigidly upon the locking rod, the tolerance problems are amplified, since additionally the space tolerances between the locking elements enter into the equation, which have, as a consequence, uneven locking forces and therewith also uneven closing forces at the ring pairs. In order to avoid such tolerance problems, individual locking springs have been assigned to each locking element in some ring binder mechanisms, which leads to a multiplication of manufacturing costs.